Polyester-polycarbonate blends useful for extrusion blow-molding

ABSTRACT

Blends of polycarbonate and copolyester that are capable of being extrusion blow-molded are described. The blends preferably comprise (I) about 1 to 99% by weight of a linear or branched polycarbonate and (II) about 1 to 99% by weight of a mixture of (i) about 40 to 100% by weight of a first copolyester and (ii) about 0 to 60% by weight of a second copolyester. The first copolyester preferably comprises (A) diacid residues comprising terephthalic acid residues, (B) diol residues comprising about 45 to 75 mole percent of 1,4-cyclohexanedimethanol (CHDM) residues and about 25 to 55 mole percent of ethylene glycol residues, and (C) about 0.05 to 1.0 mole percent of the residue of a trifunctional monomer. The optional second copolyester preferably comprises (A) diacid residues comprising terephthalic acid residues and (B) diol residues comprising about 52 to 90 mole percent of CHDM residues and about 10 to 48 mole percent of ethylene glycol residues. Preferably, the average amount of CHDM residues in the copolyester mixture II ranges from 52 to 75 mole percent. It has been surprisingly found that the presence of the trifunctional residues in the first copolyester can impart sufficient melt strength for the blends to be extrusion blow-molded. Containers and shaped articles made from the blends as well as a method of making the articles are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S.Provisional Patent Application No. 60/439,681, filed on Jan. 13, 2003,under 35 U.S.C.

119(e). The entire content of the '681 application is herebyincorporated by reference.

FIELD OF THE INVENTION

This invention generally relates to blends of polycarbonate andcopolyesters that are capable of being extrusion blow-molded. Theinvention also relates to containers and shaped articles made from theblends as well as a method of making the articles.

BACKGROUND OF THE INVENTION

Various types of containers currently made from glass are being replacedby plastic containers due to the weight, bulkiness, and susceptibilityto breakage inherent in glass containers. In many cases, thesecontainers can be manufactured from existing polymers, such as thepolyesters described in U.S. Pat. No. 4,983,711. Polyvinylchloride (PVC)and polycarbonate (PC) are other materials often used for extrusionblow-molded containers. In certain circumstances, however, thesepolymers do not meet fitness-for-use criteria when used in their neatform. For example, when the containers must contain liquids hotter than75° C., the polyesters described in the '711 patent and PVC are notadequate due to low softening points. Similarly, polycarbonate is oftenunacceptable in the same applications due to poor chemical resistance tothe contents or cleaners used during processing of the bottles. Inaddition, polycarbonate often requires complicated annealing proceduresto remove residual stresses formed during processing.

In order to take advantage of selected properties of different polymers,for example, high temperature resistance and good chemical resistance,they are often blended together. However, not all blends aretransparent; thus, the selection of materials that can be blendedtogether is further limited by the need to create transparentcontainers.

Blends of polycarbonate and certain polyesters are used in injectionmolding and sheet extrusion applications. These blends are clear and canprovide a good balance of chemical resistance and heat resistance.However, existing commercial transparent blends of polycarbonate andpolyesters cannot be processed by extrusion blow-molding due to lack ofmelt strength.

Manufacturing equipment and processes have been designed and put intouse for the cost-efficient production of various types and sizes ofcontainers at high rates. One of these manufacturing processes isextrusion blow-molding wherein a polymer melt is extruded from a diedownward in the shape of a hollow cylinder or tube. Bottles and othershaped articles are produced by clamping a mold around the molten,hollow cylinder and injecting a gas, e.g., air, into the molded-encasedcylinder to force the molten polymer into the mold. For a polymer to beuseful in extrusion blow-molding processes, the polymer should possesssufficient melt strength. To be useful for the production of rigid(self-supporting) containers, especially relatively large containers,e.g., containers intended for packaging volumes of 3 L or greater, andcontainers having an irregular shape, the polymer should also possessadequate physical, tensile, and thermal properties.

Many polymeric materials do not possess melt strength sufficient torender them suitable for extrusion blow-molding, and when extrudeddownward from a die, the polymer melt drops rapidly and forms a thinstring and/or breaks. Polymers suitable for extrusion blow-molding havea melt strength that is sufficient to support the weight of the polymer.Good melt strength is desired for the manufacture by extrusionblow-molding of containers having uniform wall thickness.

Since melt strength is related to slow flow, which is induced primarilyby gravity, melt strength can be related to the viscosity of a polymermeasured at a low shear rate, such as 1 radian/second. Viscosity can bemeasured by typical viscometers, such as a parallel plate viscometer.Typically, viscosity is measured at the typical processing temperaturefor the polymer and is measured at a series of shear rates, oftenbetween 1 radian/second and 400 radian/second. In extrusionblow-molding, the viscosity at 1 radian/second at processingtemperatures typically needs to be above 30,000 poise in order to blow abottle. Larger parisons require higher viscosities.

Melt strength, however, only defines one of the polymer processingcharacteristics desired in extrusion blow-molding. Another desiredcharacteristic is the ease of flow at high shear rates. The polymer is“melt processed” at shear rates ranging anywhere from about 10 s⁻¹ to1000 s⁻¹ in the die/extruder. A typical shear rate encountered in thebarrel or die during extrusion blow-molding or profile extrusion is 400radians/second. These high shear rates are encountered as the polymerflows down the extruder screw, or as it passes through the die. Thesehigh shear rates are desired to maintain reasonably fast productionrates. Unfortunately, high melt viscosity at high shear rates can leadto viscous dissipation of heat, in a process referred to as shearheating. Shear heating raises the temperature of the polymer, and theextent of temperature rise is directly proportional to the viscosity atthat shear rate. Since viscosity decreases with increasing temperature,shear heating decreases the low shear rate viscosity of the polymer, andthus, its melt strength decreases.

Furthermore, a high viscosity at high shear rates (for example, as foundin the die) can create a condition known as melt fracture or “sharkskin”on the surface of the extruded part or article. Melt fracture is a flowinstability phenomenon occurring during extrusion of thermoplasticpolymers at the fabrication surface/polymer melt boundary. Theoccurrence of melt fracture produces severe surface irregularities inthe extrudate as it emerges from the orifice. The naked eye detects thissurface roughness in the melt-fractured sample as a frosty appearance ormatte finish as opposed to an extrudate without melt fracture thatappears clear. Melt fracture can occur whenever the wall shear stress inthe die exceeds a certain value, typically 0.1 to 0.2 MPa. The wallshear stress is directly related to the volume throughput or line speed(which dictates the shear rate) and the viscosity of the polymer melt.By reducing either the line speed or the viscosity at high shear rates,the wall shear stress is reduced, lowering the possibility for meltfracture to occur. Although the exact shear rate at the die wall is afunction of the extruder output and the geometry and finish of thetooling, a typical shear rate that is associated with the onset of meltfracture is 400 radian/sec. Likewise, the viscosity at this shear ratetypically needs to be below 10,000 poise.

To couple all of these desired properties, the ideal extrusionblow-molding polymer, from a processability standpoint, will possess ahigh viscosity at low shear rates in conjunction with a low viscosity athigh shear rates. Fortunately, most polymers naturally exhibit at leastsome degree of viscosity reduction between low and high shear rates,known as “shear thinning”, which aids in their processability. Based onthe preceding discussion, one definition of shear thinning relevant toextrusion blow-molding would be the ratio of the viscosity measured at 1radian/second to the viscosity measured at 400 radians/second when bothviscosities are measured at the same temperature. The measurementtemperature selected should be typical of the actual processingconditions and one that provides a viscosity of 10,000 poise or less at400 rad/sec. This definition will be used to describe shear thinning forthe purposes of this invention. Based on the preceding discussion, agood extrusion blow-molding material would possess a shear thinningratio of 3.0 or higher when measured at a temperature that provides aviscosity at 400 rad/sec of 10,000 poise or less.

SUMMARY OF THE INVENTION

In one aspect, the invention relates to a blend that is capable of beingextrusion blow-molded. The blend comprises:

-   -   I. about 1 to 99 weight percent of a polycarbonate comprising a        diol component comprising about 90 to 100 mole percent of        4,4′-isopropylidenediphenol units and about 0 to 10 mol percent        modifying diol units having 2 to 16 carbon atoms; and    -   II. about 1 to 99 weight percent of a mixture comprising:        -   A. about 40 to 100 weight percent of a first copolyester            that preferably has an inherent viscosity of about 0.5 to            1.1 and a shear thinning ratio of at least about 5, and            comprises:            -   (1) diacid residues comprising terephthalic acid                residues;            -   (2) diol residues comprising about 45 to 75 mole percent                of 1,4-cyclohexanedimethanol residues and about 25 to 55                mole percent of ethylene glycol residues; and            -   (3) about 0.05 to 1.0 mole percent of the residue of a                trifunctional monomer; and        -   B. about 0 to 60 weight percent of a second copolyester            comprising:            -   (1) diacid residues comprising terephthalic acid                residues; and            -   (2) diol residues comprising about 52 to 90 mole percent                1,4-cyclohexanedimethanol residues and about 10 to 48                mole percent ethylene glycol residues,    -   wherein the average amount of 1,4-cyclohexanedimethanol residues        in the first and second copolyesters is between 52 to 75 mole        percent.

In a preferred embodiment, the blend comprises between 45 and 90 weightpercent of the copolyester mixture and between 10 and 55 weight percentof the polycarbonate, and the first copolyester preferably has aninherent viscosity of about 0.5 to 1.1 and a shear thinning ratio of atleast about 5, and comprises:

-   -   A. diacid residues comprising terephthalic acid residues;    -   B. diol residues comprising about 52 to 75 mole percent of        1,4-cyclohexanedimethanol residues and about 25 to 48 mole        percent of ethylene glycol residues; and    -   C. about 0.05 to 1.0 mole percent of the residue of a        trifunctional monomer.

In another aspect, the invention relates to a method of making a cleararticle. The method comprises the steps of:

-   -   (a) blending a polycarbonate, a first copolyester, and        optionally a second copolyester;    -   (b) before, during, or after step (a), melting the        polycarbonate, the first copolyester, and optionally the second        copolyester to form a melt blend; and    -   (c) cooling the melt blend to form a clear article.

In another aspect, the invention relates to shaped articles extrusionblow-molded from the blends according this invention.

In yet another aspect, the invention relates to containers extrusionblow-molded from the blends according this invention.

DETAILED DESCRIPTION OF THE INVENTION

It has been surprisingly found that certain copolyesters can be blendedwith polycarbonate to provided sufficient melt strength for extrusionblow-molding. The resultant blends are clear and do not produce problemswith crystallization during the extrusion blow-molding process.Preferably, the blends have a shear thinning ratio of at least about 3and are comprised of (A) about 1 to 99% (more preferably, 10 to 55%) byweight of a linear or branched polycarbonate and (B) about 1 to 99%(more preferably, 45 to 90%) by weight of a mixture of 40 to 100% byweight of a first copolyester and 0 to 60% by weight of a secondcopolyester. Preferably, the average amount of 1,4-cyclohexanedimethanolresidues in the mixture of the first copolyester and the secondcopolyester ranges from 52 to 75 mole percent.

The first copolyesters provided by our invention preferably have aninherent viscosity of about 0.5 to 1.1 and a shear thinning ratio of atleast about 5, and are comprised of:

-   -   A. diacid residues comprising terephthalic acid residues;    -   B. diol residues comprising about 45 to 75 mole percent        1,4-cyclohexanedimethanol residues and about 25 to 55 mole        percent ethylene glycol residues; and    -   C. about 0.05 to 1.0 mole percent of the residue of a        trifunctional monomer.

An especially preferred group of the first copolyesters has an inherentviscosity of about 0.6 to 0.9 and a shear thinning ratio of at leastabout 5, and comprises:

-   -   A. diacid residues consisting essentially of terephthalic acid        residues;    -   B. diol residues consisting essentially of about 52 to 75 mole        percent of 1,4-cyclohexanedimethanol residues and about 25 to 48        mole percent of ethylene glycol residues; and    -   C. about 0.1 to 0.25 mole percent of trimellitic acid or        anhydride residues.

An optional second copolyester provided by our invention preferably hasan inherent viscosity of about 0.5 to 1.1 and a shear thinning ratio ofat least about 2, and is comprised of:

-   -   A. diacid residues comprising terephthalic acid residues;    -   B. diol residues comprising about 52 to 90 mole percent        1,4-cyclohexanedimethanol residues and about 10 to 48 mole        percent ethylene glycol residues.

These copolyesters have been found to be useful for making blends withpolycarbonate that can be extrusion blow-molded to produce transparent,noncrystalline articles such as containers. These containers exhibitgood resistance to deformation when filled with liquids heated up to 85°C., and some compositions exhibit good resistance to deformation whenfilled with liquids heated up to 100° C. (boiling point of water). Ithas been surprisingly found that the presence of the trifunctionalresidues in the first copolyester can impart sufficient melt strengthfor the blends to be extrusion blow-molded even when non-branchedpolycarbonate is used in the blends.

Preferably, diacid residues A contain at least 40 mole percent, and morepreferably 100 mole percent, of terephthalic acid residues. Theremainder of the diacid component A may be made up of one more alicyclicand/or aromatic dicarboxylic acid residues commonly present inpolyesters. Examples of such dicarboxylic acids include 1,2-, 1,3- and1,4-cyclohexanedicarboxylic; 2,6- and 2,7-naphthalenedicarboxylic;isophthalic; and the like. Diacid residues A may be derived from thedicarboxylic acids or from ester forming derivatives thereof such asdialkyl esters or acids chlorides.

The trifunctional residues C can be derived from tricarboxylic acids orester forming derivatives thereof such as trimellitic(1,2,4-benzenetricarboxylic) acid and anhydride, hemimellitic(1,2,3-benzenetricarboxylic) acid and anhydride, trimesic(1,3,5-benzenetricarboxylic) acid, and tricarballyic(1,2,3-propanetricarboxylic) acid. Generally, any tricarboxyl residuecontaining about 6 to 9 carbon atoms may be used as component C. Thetrifunctional residue may also be derived from an aliphatic triolcontaining about 3 to 8 carbon atoms such as glycerin,trimethylolethane, and trimethylolpropane. The amount of thetrifunctional monomer residue present in the first copolyester ispreferably in the range of about 0.10 to 0.25 mole percent. Thepreferred trifunctional monomer residues are residues ofbenzenetricarboxylic acids (including anhydrides), especiallytrimellitic acid or anhydride.

The mole percentages referred to herein are based on 100 mole percent(or the total number of moles) of the particular component in question.For example, the expression “diacid residues comprising at least 40 molepercent terephthalic residues” means that at least 40 percent of themoles of diacid residues in the copolyester are terephthalic residues.The balance of the diacid residues can be some other species. The molepercent of the trifunctional component C in the first copolyester isbased on (1) the moles of diacid component A when component C is atriacid residue or (2) the moles of diol component B when component C isa triol residue.

When the word “about” precedes a numerical range, it is intended thatthe word modifies both the lower as well as the higher value of therange.

When the blend comprises a mixture of copolyesters, an especiallypreferred group of our first copolyesters has an inherent viscosity ofabout 0.6 to 0.9 and a shear thinning ratio of at least about 5, and iscomprised of:

-   -   A. diacid residues consisting essentially of terephthalic acid        residues;    -   B. diol residues consisting essentially of about 48 to 65 mole        percent 1,4-cyclohexanedimethanol residues and about 35 to 52        mole percent ethylene glycol residues; and    -   C. about 0.1 to 0.25 mole percent of trimellitic acid or        anhydride residues.

The copolyesters of our invention may be prepared using procedures wellknown in the art for the preparation of high molecular weightpolyesters. For example, the copolyesters may be prepared by directcondensation using a dicarboxylic acid or by ester interchange using adialkyl dicarboxylate. Thus, a dialkyl terephthalate such as dimethylterephthalate is ester interchanged with the diols at elevatedtemperatures in the presence of a catalyst. Polycondensation is carriedout at increasing temperatures and at reduced pressures until acopolyester having the desired inherent viscosity is obtained. Theinherent viscosities (I.V., dl/g) reported herein were measured at 25°C. using 0.5 g polymer per 100 mL of a solvent consisting of 60 parts byweight phenol and 40 parts by weight tetrachloroethane. The molepercentages of the diol residues of the polyesters were determined bynuclear magnetic resonance.

Examples of the catalyst materials that may be used in the synthesis ofthe polyesters utilized in the present invention include titanium,manganese, zinc, cobalt, antimony, gallium, lithium, calcium, silicon,and germanium. Such catalyst systems are described in U.S. Pat. Nos.3,907,754; 3,962,189; 4,010,145; 4,356,299; 5,017,680; 5,668,243; and5,681,918, the contents of which are herein incorporated by reference intheir entirety. Preferred catalyst metals include titanium and manganeseand most preferred is titanium. The amount of catalytic metal used mayrange from about 5 to 100 ppm, but the use of catalyst concentrations ofabout 5 to 35 ppm titanium is preferred in order to provide polyestershaving good color, thermal stability, and electrical properties.Phosphorus compounds frequently are used in combination with thecatalyst metals, and any of the phosphorus compounds normally used inmaking polyesters may be used. Up to about 100 ppm phosphorus typicallymay be used.

The polycarbonate portion of the present blend preferably has a diolcomponent containing about 90 to 100 mole percent bisphenol A units, and0 to about 10 mole percent can be substituted with units of othermodifying aliphatic or aromatic diols, besides bisphenol A, having from2 to 16 carbons. The polycarbonate can contain branching agents, such astetraphenolic compounds, tri-(4-hydroxyphenyl) ethane, pentaerythritoltriacrylate and others discussed in U.S. Pat. Nos. 6,160,082; 6,022,941;5,262,511; 4,474,999; and 4,286,083. Other suitable branching agents arementioned herein below. It is preferable to have at least 95 molepercent of diol units in the polycarbonate being bisphenol A. Suitableexamples of modifying aromatic diols include the aromatic diolsdisclosed in U.S. Pat. Nos. 3,030,335 and 3,317,466.

The inherent viscosity of the polycarbonate portion of the blendsaccording to the present invention is preferably at least about 0.3dL/g, more preferably at least 0.5 dL/g, determined at 25° C. in 60/40wt/wt phenol/tetrachloroethane.

The melt flow of the polycarbonate portion of the blends according tothe present invention is preferably between 1 and 20, and morepreferably between 2 and 18, as measured according to ASTM D1238 at atemperature of 300° C. and using a weight of 1.2 kg.

The polycarbonate portion of the present blend can be prepared in themelt, in solution, or by interfacial polymerization techniques wellknown in the art. Suitable methods include the steps of reacting acarbonate source with a diol at a temperature of about 0° C. to 315° C.at a pressure of about 0.1 to 760 mm Hg for a time sufficient to form apolycarbonate. Commercially available polycarbonates that can be used inthe present invention, are normally made by reacting an aromatic diolwith a carbonate source such as phosgene, dibutyl carbonate, or diphenylcarbonate, to incorporate 100 mol percent of carbonate units, along with100 mol percent diol units into the polycarbonate. For examples ofmethods of producing polycarbonates, see U.S. Pat. Nos. 5,498,688;5,494,992; and 5,489,665, which are incorporated by reference in theirentirety.

Processes for preparing polycarbonates are known in the art. The linearor branched polycarbonate that can be used in the invention disclosedherein is not limited to or bound by the polycarbonate type or itsproduction method. Generally, a dihydric phenol, such as bisphenol A, isreacted with phosgene with the use of optional mono-functional compoundsas chain terminators and tri-functional or higher functional compoundsas branching or crosslinking agents. Reactive acyl halides are alsocondensation polymerizable and have been used in polycarbonates asterminating compounds (mono-functional), comonomers (di-functional), orbranching agents (tri-functional or higher).

One method of forming branched polycarbonates, disclosed, for example,in U.S. Pat. No. 4,001,884, involves the incorporation of an aromaticpolycarboxylic acid or functional derivative thereof in a conventionalpolycarbonate-forming reaction mixture. The examples in the '884 patentdemonstrate such incorporation in a reaction in which phosgene undergoesreaction with a bisphenol, under alkaline conditions typically involvinga pH above 10. Experience has shown that a preferred aromaticpolycarboxylic acid derivative is trimellitic acid trichloride. Alsodisclosed in the aforementioned patent is the employment of a monohydricphenol as a molecular weight regulator; it functions as a chaintermination agent by reacting with chloroformate groups on the formingpolycarbonate chain.

U.S. Pat. No. 4,367,186 disclose a process for producing cross-linkedpolycarbonates wherein a cross-linkable polycarbonate containsmethacrylic acid chloride as a chain terminator. A mixture of bisphenolA, aqueous sodium hydroxide, and methylene chloride is prepared. To thisis added a solution of methacrylic acid chloride in methylene chloride.Then, phosgene is added, and an additional amount of aqueous sodiumhydroxide is added to keep the pH between 13 and 14. Finally, thetriethylamine coupling catalyst is added.

EP 273 144 discloses a branched poly(ester)carbonate which is end cappedwith a reactive structure of the formula —C(O)—CH═CH—R, wherein R ishydrogen or C₁₋₃ alkyl. This polycarbonate is prepared in a conventionalmanner using a branching agent, such as trimellityl trichloride and anacryloyl chloride to provide the reactive end groups. According to theexamples, the process is carried out by mixing water, methylenechloride, triethylamine, bisphenol A, and optionally para-t-butyl phenolas a chain terminating agent. The pH is maintained at 9 to 10 byaddition of aqueous sodium hydroxide. A mixture of terephthaloyldichloride, isophthaloyl dichloride, methylene chloride, and optionallyacryloyl chloride, and trimellityl trichloride is added dropwise.Phosgene is then introduced slowly into the reaction mixture.

Randomly branched polycarbonates and methods of preparing them are knownfrom U.S. Pat. No. 4,001,184. At least 20 weight percent of astoichiometric quantity of a carbonate precursor, such as an acyl halideor a haloformate, is reacted with a mixture of a dihydric phenol and atleast 0.05 mole percent of a polyfunctional aromatic compound in amedium of water and a solvent for the polycarbonate. The medium containsat least 1.2 mole percent of a polymerization catalyst. Sufficientalkali metal hydroxide is added to the reaction medium to maintain a pHrange of 3 to 6, and then sufficient alkali metal hydroxide is added toraise the pH to at least 9 but less than 12 while reacting the remainingcarbonate precursor.

U.S. Pat. No. 6,225,436 discloses a process for preparing polycarbonateswhich allows the condensation reaction incorporation of an acyl halidecompound into the polycarbonate in a manner which is suitable in batchprocesses and in continuous processes. Such acyl halide compounds can bemono-, di-, tri- or higher-functional and are preferably for branchingor terminating the polymer molecules or providing other functionalmoieties at terminal or pendant locations in the polymer molecule.

U.S. Pat. No. 5,142,088 discloses the preparation of branchedpolycarbonates, and more particularly to novel intermediates useful inthe preparation and a method for conversion of the intermediates viachloroformate oligomers to the branched polycarbonates. One method formaking branched polycarbonates with high melt strength is a variation ofthe melt-polycondensation process where the diphenyl carbonate andBisphenol A are polymerized together with polyfunctional alcohols orphenols as branching agents.

DE 19727709 discloses a process to make branched polycarbonate in themelt-polymerization process using aliphatic alcohols. It is known thatalkali metal compounds and alkaline earth compounds, when used ascatalysts added to the monomer stage of the melt process, will not onlygenerate the desired polycarbonate compound, but also other productsafter a rearrangement reaction known as the “Fries” rearrangement. Thisis discussed in U.S. Pat. No. 6,323,304. The presence of the Friesrearrangement products in a certain range can increase the melt strengthof the polycarbonate resin to make it suitable for bottle and sheetapplications. This method of making a polycarbonate resin with a highmelt strength has the advantage of having lower raw material costscompared with the method of making a branched polycarbonate by adding“branching agents.” In general, these catalysts are less expensive andmuch lower amounts are required compared to the branching agents.

JP 09059371 discloses a method for producing an aromatic polycarbonatein the presence of a polycondensation catalyst, without the use of abranching agent, which results in a polycarbonate possessing a branchedstructure in a specific proportion. In particular, JP 09059371 disclosesthe fusion-polycondensation reaction of a specific type of aromaticdihydroxy compound and diester carbonate in the presence of an alkalimetal compound and/or alkaline earth metal compound and/or anitrogen-containing basic compound to produce a polycarbonate having anintrinsic viscosity of at least 0.2. The polycarbonate is then subjectto further reaction in a special self-cleaning style horizontal-typebiaxial reactor having a specified range of the ratio L/D of 2 to 30(where L is the length of the horizontal rotating axle and D is therotational diameter of the stirring fan unit). JP 09059371 teaches theaddition of the catalysts directly to the aromatic dihydroxy compoundand diester carbonate monomers.

U.S. Pat. No. 6,504,002 discloses a method for production of a branchedpolycarbonate composition, having increased melt strength, by lateaddition of branch-inducing catalysts to the polycarbonate oligomer in amelt polycondensation process, the resulting branched polycarbonatecomposition, and various applications of the branched polycarbonatecomposition. The use of polyhydric phenols having three or more hydroxygroups per molecule, for example, 1,1,1-tris-(4-hydroxyphenyl)ethane(THPE), 1,3,5-tris-(4-hydroxyphenyl)benzene,1,4-bis-[di-(4-hydroxyphenyl)phenylmethyl]benzene, and the like, asbranching agents for high melt strength blow-moldable polycarbonate 30resins prepared interfacially has been described in U.S. Pat. Nos. Re.27,682 and 3,799,953.

Other methods known to prepare branched polycarbonates throughheterogeneous interfacial polymerization methods include the use ofcyanuric chloride as a branching agent (U.S. Pat. No. 3,541,059),branched dihydric phenols as branching agents (U.S. Pat. No. 4,469,861),and 3,3-bis-(4-hydroxyaryl)-oxindoles as branching agents (U.S. Pat. No.4,185,009). Additionally, aromatic polycarbonates end-capped withbranched alkyl acyl halides and/or acids and said to have improvedproperties are described in U.S. Pat. No. 4,431,793.

Trimellitic triacid chloride has also been used as a branching agent inthe interfacial preparation of branched polycarbonate. U.S. Pat. No.5,191,038 discloses branched polycarbonate compositions having improvedmelt strength and a method of preparing them from aromatic cyclicpolycarbonate oligomers in a melt equilibration process.

The novel polymer blends of the present invention preferably contain aphosphorus catalyst quencher component, typically one or more phosphoruscompounds such as a phosphorus acid, e.g., phosphoric and/or phosphorousacids, or an ester of a phosphorus acid such as a phosphate or phosphiteester. Further examples of phosphorus catalyst quenchers are describedin U.S. Pat. Nos. 5,907,026 and 6,448,334. The amount of phosphoruscatalyst quencher present typically provides an elemental phosphoruscontent of about 0 to 0.5 weight percent, preferably 0.1 to 0.25 weightpercent, based on the total weight of the blend.

The blends may also include other additives, such as heat stabilizers,UV stabilizers, antioxidants, UV absorbers, mold releases, biocides,plasticizers, or fillers such as clay, mica, talc, ceramic spheres,glass spheres, glass flakes, and the like. Additives such as these aretypically used in relatively small quantities. These additives may beincorporated into the blends of the invention by way of concentrates.These concentrates may use polyesters that are not of the compositiondescribed above. If so, these other polyesters are preferably not addedin quantities exceeding 5 weight percent.

The blends may be prepared using procedures well known in the artincluding, but not restricted to, compounding in a single screwextruder, compounding in a twin screw extruder, or simply pelletblending the components together prior to extrusion blow-molding.

A typical method of preparing the blends involves 1) adding pellets ofthe polycarbonate, the first copolyester, and optionally the secondcopolyester to an extruder using additive feeders, melt feeders or bypreblending the pellets; 2) melting the polycarbonate, the firstcopolyester, and optionally the second copolyester in the extruder; 3)blending the polycarbonate, the first copolyester, and optionally thesecond copolyester by shearing action of the extruder screw to form amelt blend; and 4) cooling the melt blend to form clear pellets. Thetemperature settings of the extruder should be set at greater than 230°C., preferably greater than 250° C. The compounding process may useeither a single or twin screw extruders. Alternatively, the pellets ofthe polycarbonate, the first copolyester, and optionally the secondcopolyester may be placed directly into the extruder used to extrusionblow-mold the final articles, without a prior compounding step.

Known extrusion blow-molding techniques may be used to make shapedarticles or containers from the polymer blends of the present invention.A typical extrusion blow-molding manufacturing process involves: 1)melting the resin in an extruder; 2) extruding the molten resin througha die to form a tube of molten polymer (i.e., a parison) having auniform side wall thickness; 3) clamping a mold having the desiredfinished shape around the parison; 4) blowing air into the parison,causing the extrudate to stretch and expand to fill the mold; 5) coolingthe molded article; and 6) ejecting the article from the mold.

The polymer blends of the present invention are characterized by a novelcombination of properties including low haze. Haze can be determined bytwo methods. The first method is visual observation of the blendextrudate where about 300 grams of the melt blended material iscollected in a pile and set aside and allowed to slowly cool to roomtemperature. The pile of cooled blend is then examined visually forhaze. The second method measures haze according to ASTM D1003 onextrusion molded bottle sidewalls using a HunterLab UltraScan Sphere8000. % Haze=100 * Diffuse Transmission/Total Transmission. Diffusetransmission is obtained by placing a light trap on the other side ofthe integrating sphere from where the sample port is, thus eliminatingthe straight-through light path. Only light scattered by greater than2.5 degrees is measured. Total transmission includes measurement oflight passing straight-through the sample and also off-axis lightscattered to the sensor by the sample. The sample is placed at the exitport of the sphere so that off-axis light from the full sphere interioris available for scattering. (Regular transmission is the name given tomeasurement of only the straight-through rays—the sample is placedimmediately in front of the sensor, which is approximately 20 cm awayfrom the sphere exit port—this keeps off-axis light from impinging onthe sample.)

The melt viscosity of the materials used herein is measured at 240° C.and is determined with a Rheometrics Mechanical Spectrometer (RMS 800)with 25 mm parallel plates. Samples are vacuum dried at 70° C. overnightor longer before testing. The units are reported in Poise (P).

The glass transition temperatures (Tgs) of the blends were determinedusing a TA Instruments 2950 differential scanning calorimeter (DSC) at ascan rate of 20° C./minute. The values reported below are from thesecond DSC scan.

EXAMPLES

The polymer blends provided by the present invention and the preparationthereof, including the preparation of representative polyesters, arefurther illustrated by the following examples.

Comparative Examples 1-3 and Examples 1-5

Blends were prepared by combining polyester with polycarbonate and aphosphorus additive. A summary of materials used is shown in Table 1.

The copolyesters and polycarbonates used in the blends are listed belowand were prepared by methods well known in the art for the preparationof high molecular weight polyesters.

Copolyester A is a branched copolyester comprising a diacid componentcontaining 100 mole percent terephthalic acid residues and a diolcomponent containing 59-63 mole percent 1,4-cyclohexanedimethanol (CHDM)residues and 37-41 mole percent ethylene glycol residues and alsocontaining 0.18 mole percent trimellitic anhydride (TMA) residues.

Copolyester B is a branched copolyester comprising a diacid componentcontaining 100 mole percent terephthalic acid residues and a diolcomponent containing 56 mole percent CHDM residues and 44 mole percentethylene glycol residues and also containing 0.18 mole percent TMAresidues.

Copolyester C is a branched copolyester comprising a diacid componentcontaining 100 mole percent terephthalic acid residues and a diolcomponent containing 48-52 mole percent CHDM residues and 52-48 molepercent ethylene glycol residues and also containing 0.18 mole percentTMA residues.

Copolyester D is a linear copolyester comprising a diacid componentcontaining 100 mole percent terephthalic acid residues and a diolcomponent containing 62 mole percent CHDM residues and 38 mole percentethylene glycol residues.

Copolyester E is a linear copolyester comprising a diacid componentcontaining 100 mole percent terephthalic acid residues and a diolcomponent containing 81 mole percent CHDM residues and 19 mole percentethylene glycol.

Polycarbonate X is a linear polycarbonate produced by Dow ChemicalCompany under the commercial name Calibre 300-10. It has a melt flowrate (MFR) of 10 measured according to ASTM D1238 at 300° C. using a 1.2kg mass.

Polycarbonate Y is a branched polycarbonate produced by Dow ChemicalCompany under the commercial name Calibre 603-3. It has a melt flow rate(MFR) of 3 measured according to ASTM D1238 at 300° C. using a 1.2 kgmass.

The phosphorus concentrate (designated “conc” in Table 1) was preparedby first compounding Weston 619, a distearyl pentaerythritol diphosphiteavailable from GE Specialty Plastics, into copolyester D on a singlescrew extruder at 270° C. This composition is then tumble-blended with 5wt % water at 80° C. for 8 hours to hydrolyze the Weston 619. The finalphosphorus content of the pellets is 5 weight percent elementalphosphorus based on total pellet weight.

All blends were prepared on a Sterling 1.25 inch single screw extruderat 260° C. melt temperature and 90 rpm. The copolyesters were dried at70° C., and the bisphenol A polycarbonate was dried at 120° C.overnight. In each blend example, 57 parts by weight of the copolyesterswere combined with 40 parts by weight bisphenol A polycarbonate and 3parts by weight of the phosphorus additive, except for ComparativeExample 2 where 47 parts by weight of the copolyester were combined with50 parts by weight bisphenol A polycarbonate and 3 parts by weight ofthe phosphorus additive.

Comparative Example 1 is an example of neat copolyester C. This materialhas a good shear thinning ratio, but does not possess a sufficientlyhigh glass transition temperature (Tg) for high heat applications.

Comparative Example 2 is an example of a blend that does not contain anybranched copolyester. This blend does possess a sufficiently high glasstransition temperature for high heat applications, but does not have ahigh enough shear thinning ratio to be blown into bottles.

Comparative Example 3 is an example of a blend of polycarbonate with acopolyester that has too low a level of CHDM. This blend is hazy.

Examples 1-5 are examples of the invention that possess high glasstransition temperatures, possess good shear thinning ratios, and arefree of haze.

TABLE 1 Avg. Melt viscosity at 240° C. mole Shear CPE CPE CPE CPE CPE %PC PC Tg Haze 1 400 thinning Ex. A B C D E CHDM X Y Conc (° C.) (visual)rad/sec rad/sec ratio CE-1 100 50 83 clear 47000 8400 5.60 CE-2 47 81 503 113 clear 17100 8700 1.97 CE-3 57 50 40 3 hazy 31200 9000 3.47 E-1 5756 40 3 clear E-2 57 62 40 3 clear 39300 10000 3.93 E-3 57 59 40 3 105clear 46300 9800 5.55 E-4 32 25 64 40 3 106 clear 36300 9700 3.75 E-5 3225 56 40 3 104 clear 38300 9800 3.91

Comparative Example 4

Bottles were generated from the blends prepared in Comparative Example 3using an 80 mm Bekum H-121 continuous extrusion blow-molding machinefitted with a barrier screw. The materials were dried for 12 hours at65° C. (150° F.) prior to extrusion. The extruder was run at 12revolutions per minute (RPM) using a 215° C. (420° F.) barreltemperature and a 199° C. (390° F.) head temperature. The temperature ofthe melt was 232° C. (449° F.), measured by inserting a melt probedirectly into the parison 5 mm out from the die. The materials wereextruded into water bottles having a volume of 3.785 liters (1 U.S.gallon), using a 100 mm die. The bottles weighed 175 grams. Haze in thebottle sidewall was measured to be 3.94%.

Example 6

Bottles were generated from the blend prepared in Example 1 using an 80mm Bekum H-121 continuous extrusion blow-molding machine fitted with abarrier screw. The materials were dried for 12 hours at 65° C. (150° F.)prior to extrusion. The extruder was run at 27 revolutions per minute(RPM) using a 199° C. (390° F.) barrel temperature and a 199° C. (390°F.) head temperature. The temperature of the melt was 239° C. (452° F.),measured by inserting a melt probe directly into the parison 5 mm outfrom the die. The materials were extruded into water bottles having avolume of 3.785 liters (1 U.S. gallon), using a 100 mm die. The bottlesweighed 150 grams. Haze in the bottle sidewall was measured to be 0.38%.

Example 7

Bottles were generated from the blend prepared in Example 2 using an 80mm Bekum H-121 continuous extrusion blow-molding machine fitted with abarrier screw. The materials were dried for 8 hours at 65° C. (150° F.)prior to extrusion. The extruder was run at 21 revolutions per minute(RPM) using a 200° C. (392° F.) barrel temperature and a 190° C. (375°F.) head temperature. The temperature of the melt was 218° C. (425° F.),measured by inserting a melt probe directly into the parison 5 mm outfrom the die. The materials were extruded into water bottles having avolume of 3.785 liters (1 U.S. gallon), using a 100 mm die. The bottlesweighed 150 grams. Haze in the bottle sidewall was measured to be 0.71%.

Example 8

Bottles were generated from the blend prepared in Example 3 using an 80mm Bekum H-121 continuous extrusion blow-molding machine fitted with abarrier screw containing a Maddock mixing section. The materials weredried for 8 hours at 65° C. (150° F.) prior to extrusion. The extruderwas run at 10 revolutions per minute (RPM) using a 232° C. (450° F.)barrel temperature and a 232° C. (450° F.) head temperature. Thetemperature of the melt was 249° C. (481° F.), measured by inserting amelt probe directly into the parison 5 mm out from the die. Thematerials were extruded into handleware bottles having a volume of 1.89liters (64 ounces), using a 70 mm die. The bottles weighed 120 grams.Haze in the bottle sidewall was measured to be 0.59%.

Example 9

Bottles were generated from the blend prepared in Example 4 using an 80mm Bekum H-121 continuous extrusion blow-molding machine fitted with abarrier screw containing a Maddock mixing section. The materials weredried for 8 hours at 65° C. (150° F.) prior to extrusion. The extruderwas run at 10 revolutions per minute (RPM) using a 232° C. (450° F.)barrel temperature and a 232° C. (450° F.) head temperature. Thetemperature of the melt was 250° C. (483° F.), measured by inserting amelt probe directly into the parison 5 mm out from the die. Thematerials were extruded into handleware juice bottles having a volume of1.89 liters (64 ounces), using a 70 mm die. The bottles weighed 90grams. Haze in the bottle sidewall was measured to be 0.67%.

The invention has been described in detail with particular reference topreferred embodiments and working examples, but it will be understoodthat variations and modifications can be made without departing from thespirit and scope of the invention, as defined by the following claims.

1. A visually clear blend that is capable of being extrusionblow-molded, said blend comprising a polycarbonate, at least twocopolyesters, and a phosphorus catalyst quencher; wherein the at leasttwo copolyesters have different amounts of 1,4-cyclohexandimethanolresidues from each other, but comprise an average of about 52 to 75 mole% of 1,4-cyclohexanedimethanol residues based on the total mole % ofdiol residues and about 0.05 to 1.0 mole % of the residue of atrifunctional monomer.
 2. The blend according to claim 1, whichcomprises 45 to 90 weight percent of copolyesters and 10 to 55 weightpercent of polycarbonate.
 3. The blend according to claim 2, which has ashear thinning ratio of at least about
 3. 4. The blend according toclaim 1, wherein the polycarbonate has a melt flow rate between 2 and18.
 5. The blend according to claim 1, wherein the polycarbonatecomprises a branching agent.
 6. The blend according to claim 1, whichcomprises a first copolyester and a second copolyester, wherein thefirst copolyester has an inherent viscosity of about 0.5 to 1.1 and ashear thinning ratio of at least about 5, and comprises: A. diacidresidues comprising terephthalic acid residues; B. diol residuescomprising about 45 to 75 mole percent of 1,4-cyclohexanedimethanolresidues and about 25 to 55 mole percent of ethylene glycol residues;and C. about 0.05 to 1.0 mole percent of the residue of a trifunctionalmonomer, wherein the second copolyester has an inherent viscosity ofabout 0.5 to 1.1 and a shear thinning ratio of at least about 2, andcomprises: A. diacid residues comprising terephthalic acid residues; andB. diol residues comprising about 52 to 90 mole percent1,4-cyclohexanedimethanol residues and about 10 to 48 mole percentethylene glycol residues, and wherein the average amount of1,4-cyclohexanedimethanol residues in the first and second copolyestersis between 52 to 75 mole percent.
 7. The blend according to claim 6,wherein the first copolyester comprises: A. diacid residues comprisingat least 40 mole percent of terephthalic acid residues; B. diol residuescomprising about 45 to 65 mole percent of 1,4-cyclohexanedimethanolresidues and about 35 to 55 mole percent of ethylene glycol residues;and C. about 0.05 to 1.0 mole percent of the residue of abenzenetricarboxylic acid or an hydride.
 8. The blend according to claim6, wherein the first copolyester has an inherent viscosity of about 0.6to 0.9, and comprises: A. diacid residues comprising at least 40 molepercent of terephthalic acid residues; B. diol residues comprising about45 to 75 mole percent of 1,4-cyclohexanedimethanol residues and about 25to 55 mole percent of ethylene glycol residues; and C. about 0.1 to 0.25mole percent of the residue of a benzenetricarboxylic acid or anhydride,and wherein the second copolyester has an inherent viscosity of about0.6 to 0.9, and comprises: A. diacid residues comprising terephthalicacid residues; and B. diol residues comprising about 52 to 90 molepercent 1,4-cyclohexanedimethanol residues and about 10 to 48 molepercent ethylene glycol residues.
 9. The blend according to claim 6,wherein the first copolyester has an inherent viscosity of about 0.6 to0.9, and comprises: A. diacid residues consisting essentially ofterephthalic acid residues; B. diol residues consisting essentially ofabout 48 to 65 mole percent 1,4-cyclohexanedimethanol residues and about35 to 52 mole percent ethylene glycol residues; and C. about 0.1 to 0.25mole percent trimellitic acid or anhydride residues.
 10. A shapedarticle extrusion blow-molded from the blend of claim
 1. 11. A containerextrusion blow-molded from the blend of claim
 9. 12. The blend accordingto claim 1, wherein the trifunctional monomer is selected from the groupconsisting of tricarboxylic acids or esters thereof and aliphatictriols.
 13. The blend according to claim 12, wherein the trifunctionalmonomer is a benzenetricarboxylic acid or anhydride.
 14. The blendaccording to claim 13, wherein the trifunctional monomer is trimelliticacid or anhydride.
 15. The blend according to claim 1, where in thephosphorus catalyst quencher is selected from the group consisting ofphosphoric acid, phosphorous acid, phosphate ester, and phosphite ester.16. The blend according to claim 1, wherein the phosphorus catalystquencher is present in an amount that provides an elemental phosphoruscontent of about 0.1 to 0.25 weight percent.